A lens cap is generally used for protecting an objective lens of a camera when the camera is not in use. However, when a camera includes a viewfinder optical system which operates independently of the photographic optical system, such as in the case of a direct viewing-type viewfinder, misoperation of the camera can result when the user erroneously operates the manual operating members, e.g., either the shutter release member or, when the camera includes a built-in flash device, the switching member which controls whether the camera is set to normal or flash photography conditions. This misoperation may occur because the user may not notice that the lens cap has not been removed from the front of the camera.
As a means to avoid misoperation of the camera, it has been proposed to provide a lens cap detection pin on the forward end of the camera lens barrel to detect whether or not a lens cap is mounted on the camera to lock the shutter release button upon detection of the cap. However, this structure requires the camera to be provided with a locking member for locking the shutter release member and a complex interlocking mechanism for linking the detection pin with the locking member, resulting in complexity of the mechanism, as well as an increase in camera size and in the cost of manufacture.
In a twin-lens reflex camera and the like, a lens cap has been used which covers both the photographic objective lens and the viewfinder objective lens so that a photographer, upon looking through the viewfinder, will notice the lens cap covering the lenses. However, it is impossible for such a lens cap to prevent operational errors with the camera, for example, the inadvertent depressing of the shutter release button and the resultant undesired exposure of the film when the camera is not intended to be used or the inadvertent turning on of the power switch of the electronic flash device built into the camera, causing the power source battery to be wastefully consumed.
The primary object of the present invention is to provide a very simple device which is capable of preventing any inadvertent operations of the camera when the camera is not in use.